The invention is directed to the manufacture of sheet metal shapes, particularly shapes which have two or more sections thereof disposed at right angles relative to each other. The manufacture of sheet metal often involves the bending of a metal sheet into tray-like sections having a bottom member and four upwardly extending side members disposed at right angles to the bottom member and each other. A press brake die is commonly used to shape such a tray-like member. The first set of opposing side members can be formed in the sheet metal without regard to the use of a die having a length which exceeds the length of the metal sheet. The formation of the second set of opposed side members, however, requires that the upper die, the die toward which the metal sheet is bent, be modified to accommodate the presence of the first set of opposed side members.
The modification of the upper die can be accomplished in several ways. The usual shop practices involve the removal of the long upper die and replacing it with a single shorter upper die or several shorter dies with a total length equal to or smaller than the inside dimension of the first set of opposed walls. It is also known to employ an upper die with at least one gap formed therein which is aligned to accommodate one of the side members of the first opposing set. An example of an upper die with such a gap is disclosed in U.S. Pat. No. 4,203,379. In each of the above described methods for forming the second set of opposing side members, the press brake die must undergo a set-up operation which requires the handling of a set of dies for each size panel to be manufactured. The existing methods have several obvious drawbacks such as excessive handling of die sets which causes both lost time and money. Moreover, for short run jobs in which only one or two pieces are to be manufactured, the die set-up time can often exceed the time required to effect the bending of the sheet metal by the die.